The field of the invention is automatic drill control for earth drilling machines, and more particularly to computer controlled drilling in a blast hole drill wherein drilling conditions of the blast hole drill are continuously sensed and the penetration rate and drilling rotational speed are optimized independently.
Various prior art systems have been developed utilizing computers to automatically control large drilling apparatus. For example, in the Zhukovsky, et al. U.S. Pat. No. 4,354,233 a computer is utilized in conjunction with a blast hole drill for computing the value of drilling hole penetration for a single revolution. The computer is connected to means for comparing the current value of a drilling tool penetration per single revolution with preset values. The computer is connected with its inputs to transducers and setters of input parameters, such as rotation frequency, axial load, torque, and the vibration speed of a rotary drill. In the Rogers U.S. Pat. No. 4,165,789 a control algorithm and a microcomputer is employed with a memory to maintain a maximum rate of penetration for drilling roof bolt holes. Optimization is based on regulating drill revolutions per minute and thrust while holding one of those parameters constant and varying the other. Control systems for blast hole drills are also described in U.S. Pat. Nos. 3,581,830; 3,593,807 and 3,613,805 with the Nos. '830 and '805 patents being commonly assigned. In the No. '830 patent the control system balances rotary torque and downfeed force to reduce downfeed speed when torque feedback exceeds a predetermined value. Signals derived from both torque and drilling rate are utilized in the No. '807 patent to provide optimum efficiency of operation. Automatic depth control is provided in the control system described in the No. '805 patent as well as automatic shut down.
Although automatic drill control systems have been constructed and used, they have not been employed to optimize the automatic drilling of a blast hole in the most efficient manner. One of the prior art systems is directed toward optimizing drilling rates by holding certain drilling parameters constant while varying others in search of optimization. Another compares torque with a signal which may in part be based on human experience and effects a further signal to control through the motor drive a downward pressure on the drill so that a maximum drilling rate can be obtained through strata of various and different composition.
It is an advantage of the present invention to provide an improved control system for drilling subterranean holes.
It is another advantage of this invention to provide a drill control system of the foregoing type which effects optimization in an automatic manner.
It is still another advantage of this invention to provide a control system of the foregoing type which can provide a maximum penetration rate within restraints of the blast hole drill (BHD).
It is yet another advantage of the present invention to provide a control system of the foregoing type which results in reduced maintenance and down time through efficient and proper operation of the BHD.
It is still another advantage of this invention to provide a control system of the foregoing type which can be readily adapted to currently used BHDs.